I have a 20g tank that has been set up for over 6 weeks now. After i had trhe tank it sat and cycled for 2 weeks. The first fish that i added were 3 Zebra Danio's. Since then i have added 3 platy's they died. Then about a week after they died i added 2 green swordtail and they died then i added 2 more swordtails and a masked cory, and you guessed it they died. My danio's seem to be completely healthy. I can't firgure out why my fish keep dying. I have the water checked for everything everytime i go back to the petstore to get new fish. The guy there can't seem to figure it out cause my water is fine. Please help me and the fish that i seem to be compulsively killing.

Ok, first buy your self a liquid test kit. Its much easier and its key to the fish hobby. API liquid mater test kit is what pretty much everyone here uses. It tests for pH, ammonia, nitrites, and nitrates.

Do you know what your exact water parameters are? Or do they tell you "it's fine"? How do you add these fish to your tank? And do they show any symptoms before they die? A little more information is needed before we can help you out.

your supposed to sit the fish bag with the fish in it, on top of the tank water, so the bag will get the same temperature as the water, and slowly add drops of water from the tank to the bag over half an hour until there is double amount of water as there was at the start... Then you can grab the fish out with a net and put them in. If you throw all the water from the bag in, you could get a disease that was in the LFS's tank, you don't want that happening.

Some people even quarantine their fish before putting them in the intentioned tank, not a necessity but merely a precaution.

Non-proper fish acclimation is the only reason I can figure that only your Danios survived... And i'm not surprised your danios survived either, they are one of the hardiest fish i've come across...

We had a similar problem at my LFS. All of our parameters were in a decent range (we have really hard water), but our fish loss was fairly high. We sent some water out to be tested and turns out that we have copper in the system. Apparently, Top Fin water conditioner removes copper. We used it and our loss went WAY down. With 132 tanks, we were having less than a dozen fish die, before we were about twice that. We had days were only one or two would die. Copper could be part of the problem, but most likely it is something simple. Have your water tested and ask them to write down your parameters. Also, pictures help too.

thanks for the help guys, i'm gonna go out and get that test kit soon probably tomorrow and then i'll let you know what the parameters are. also thanks for the warm welcome and the help. i also have really hard water but i don't know about the copper, i'm gonna try the top fin water conditioner, so far i've been using amquel. And as far as introducing my fish to my tank what i usually do is sit the bag in the water for about 15-20 minutes and then use i net to get my fish outta the bag and into my tank. I make sure never to let any of the water from the bag into my tank. As far as symptoms usually they will just seem lethargic and stay near the bottom and hide a lot, the last swordtail that died did have pop-eye and also i had a recent infection of ich which i treated for. Once again thanks for the help guys, I'll be back hopefully tomorrow after testing my water to let you know how it went.

Great!! Glad to hear your getting a test kit, I think you'll find it will help out a lot.

Its sounds like maybe your fish store isn't the greatest, ich, pop-eye gosh whats next? Are you still battling the ich? What treatment did you use? Its best to use salt and heat when treating for ich unless you have fish that do not tolerate salt (Your cory cat) The ich is definitely your pet stores fault, but the pop-eye could be a combo of the stress from the disease and treatment, or poor water quality, or even worse... Both.

You introduced the fish correctly for the most part. Next time after floating the bag to get the temps right, slowly add your tank water to the bag so half the bag water is from your tank and the other half is the water they came in. This will reduce the shock of introducing them to your tank. Good call on not putting the water from the store in your tank though!

Top Fin is Petsmart's brand name for fish products, and usually their quality is a bit...sub-par. Surprisingly, their water conditioner is really pretty decent, but I still don't think it's as good as Amquel. I'd stick with what you're using.

next time i buy fish i think i'll try a mega store to buy my fish since the ich would've came from the pet store, and i treated the ich with ich-out which is what they told me i should use and i am no longer treating for it. I finally got my test kit and my readings were, PH-7.4, Ammonia-.25, Nitrite-5 and, Nitrate-5. It looks like i'm gonna stop getting my water tested by that fish store too cause they were telling me the whole time that my ph was closer to 7 than to 7.4 and the last time i had it tested was only about 2 weeks ago. So once again thanks for your help guys and any more help would be very greatful.

That looks like your cycle still isn't finished. I would do a water change right away since nitrite levels of 5ppm are really dangerous to your fish. If I were in your situation, I wouldn't add anymore fish until a week or so after the ammonia and nitrite both hit (and stay at) zero.

Yikes!!! 5ppm nitrites? Water changesss!!! For the next little bit you'll want to keep a really close eye on your water parameters and when the ammonia and nitrite levels build up to much do a water change. You may end up doing almost daily water changes. But just small ones. I'm really surprised even your danios survived that